Various embodiments of forging assemblies are known for forging long axially symmetric workpieces such as by stretching and round kneading. In such forging assemblies, a hydraulic driving system is generally used requiring switch elements arranged in the usual manner remote from the piston-cylinder units. The hydraulic switch elements are operated electromagnetically. Due to the electromagnetic excitation with each switching operation and the switching element arrangement at a point remote from the piston-cylinder unit, the resultant times of switching and pressure build-up for each movement restrict the achievable stroke frequencies of such known forging assemblies to a low level. Moreover, with the prior art forging assemblies, the circuit system and total machine is very complex and expensive to produce and operate.
In known hydraulic driving systems, the working stroke and respective end positions of the piston are usually defined by solid, mechanical end stops or, optionally, by path-dependent controls. Such a design generally implies the disadvantage that the required accurate setting or control of the working piston stroke not only concerning its final positions, but also concerning its speed, is not possible by hydraulic means.
In a multi-ram forging assembly, the plurality of working cylinders are expected to operate absolutely synchronously and with identical stroke lengths. Coupling the working cylinders at the driven side to accomplish this purpose is a significant problem. Known working cylinder designs coupled to accomplish such synchronous movements cannot be adjusted and cannot be controlled to obtain identical stroke lengths for each of the total number of working cylinders. If the stroke is performed, it may not be influenced with the required regulating accuracy and the extent of movement and synchronism.
This problem is magnified with large volume working cylinders. Until now, it has not been possible to interconnect a plurality of large diameter working cylinders with closed position and/or speed control systems so that a synchronism may be achieved with respect to the several control systems required to operate a multi-ram forging assembly in such a case.